Word or text processing systems having interactive display terminals permitting an operator to extensively edit and format alphanumeric data which is, in turn, printed out on an associated printer have been in ever increasing demand in the office products and systems field. A goal of all word processing systems is to facilitate the preparation of such formatted correspondence and other documents by the systems operator. To this end, the industry has been attempting to make the processor as "friendly" and unconfusing to the operator as possible. This of course entails minimizing the operator steps necessary to produce a document and particularly minimizing constraints upon the operator.
Most current word processing systems utilize impact printers having a removable type or character font element mounted upon a carrier which is movable along horizontal lines in the document to be printed in the printer. This removable type font element may be of the ball type used throughout the industry or of the daisy wheel type having a plurality of character petals as described with respect to the printer in U.S. Pat. No. 4,178,108. It is very often the case that in preparing a document, a plurality of type font elements have to be used. Since there are in the order of from 90 to 100 characters on a font element, it is readily seen that changes of the type font element may be required even in the formation of a straightforward piece of correspondence. Portions of the document may require fonts with bold face type, other portions of the document italics fonts and still others symbol fonts to be used in equations.
In conventional practice, where a plurality of fonts have to be used to produce a given document, fonts are changed when a line or a paragraph is completed. This change is accomplished either by a message on an interactive display screen indicating to the operator that the operation of the printer has been inhibited until the operator manually changes from a given font to another selected font. At this point, the printing can be continued. On the other hand, the change of font may be accomplished through the expedient of an automatic font changer associated with the printer. U.S. Pat. No. 4,307,968 gives the details of such an automatic font changer associated with a print wheel type of printer. In the case of such an automatic font changer operation, no operator intervention is necessary; the printer automatically changes fonts in an operation which is transparent to the operator.
With reference to FIG. 17 for the following structural and operational description of font changing apparatus 270, apparatus 270 is utilized for automatically effecting an exchange of print elements in cartridge 300. A printer frame is made up of sides 264 and 265 secured together by escapement rails 266 and 267 and a top support rail 269. Mounted on escapement rails 266 and 267 is a carrier generally designated by reference numeral 290. Carrier 290 is for carrying a selection motor (not shown) within a carrier 262. Carrier 262 is for in turn carrying print element cartridge 300. Carrier 290 and thus carrier 262 are translated along platen 263 by a lead screw 230.
Top support rail 269 in addition to supporting printer frame sides 264 and 265 is used for supporting hangers 271 and 272. Hangers 271 and 272 carry font changing apparatus 270.
Integral with hangers 271 and 272 are plates 295 and 296. Plates 295 and 296 carry support means (not shown) for drive motor 280, pulleys, 275, 276, 277 and 278, and worm gear brackets 293 and 297. Carried in turn by worm gear brackets 293 and 297 are worm gears 273 and 298. Followers (not shown) connect worm gears 273 and 298 and L-shaped uprights 292 and 294, respectively. Integral with uprights 292 and 294 is an elongated and horizontally disposed rack 291. Rack 291 is vertically oriented, and vertically elevatable and lowerable upon rotation of worm gears 273 and 298. Worm gates 273 and 298 are rotatable by motor 280 through pulleys 275, 276, 277, and 278 and belts 281, 279 and 274. Belt 281 is looped over the shaft (not shown) of motor 280, and around pulley 278. Belt 279 is looped around pulleys 278 and 277. Belt 274 is looped around pulleys 277, 275, and 276. Worm gears 273 and 298 form shafts for pulleys 276 and 277, respectively.
While there are available print systems which permit changes in font between successive lines, we are not aware of any printing systems providing for changes in font in the course of a single line and particularly when such changes in font results in a change in the pitch of characters printed along this single line. The result is an additional constraint on the operator. In many existing printing systems, formatting selections made by the operator which will result in changes in font during a course of printing a single line are not permitted. In this manner, the system and consequently the operator need not be concerned with whether such changes in fonts produce pitch changes. The prior art has apparently not developed the capability of handling pitch changes which occur in a single line, i.e., printing on the same line with fonts of different pitch. Thus, even if existing equipment would permit font changes, the operator would be bound by the constraint of changing to a font of the same pitch. This would present significant constraints on the operator as well as being a more costly system. For example, suppose that an operator wished to italicize a portion of a single line. Since the regular portion of the line could conceivably be printed with a font having one of three possible pitches, i.e., 10 pitch, 12 pitch and 15 pitch, the printer would then have to inventory italics fonts of 10, 12 and 15 pitch. This would appear to be unnecessarily costly for the equipment to inventory three different font elements for rarely used italics printing.
The printer system of the present invention, provides for the use of different font elements of different pitch in the same line to thereby eliminate the operator constraint limitation as well as the potential costly font element inventories required of systems which cannot accept the use of fonts of different pitch to print a single line.